Extended Whipple’s index to measure the quality of travel surveys using rounding in reported time: A comparison in developing countries

Abstract

This study proposes a weighted rounded departure time (wRDT) index to measure the quality of travel surveys. This index is an extension of Whipple’s index, used in demographic studies to measure age heaping. A comparison was made between the quality of 23 travel surveys conducted by Japan International Cooperation Agency in developing countries using the proposed index, and the differences in the rounding in the reported trip departure times were analyzed. The result yielded three findings. First, age heaping in the travel surveys was higher than that in the census in most cities. Second, rounding departure time to 15 min steps was fewer in East Asian cities. Finally, age heaping and departure time rounding to 60 min were higher in South Asian and African cities. Furthermore, a comparison of wRDT indices between both genders indicated a difference in rounding: female respondents were less likely to round their responses than males.